Urocitellus elegans 357their fi rst hibernation was positively associated with the
amount of winter snow and the time their mothers stayed
alive past weaning, and negatively linked to summer tem-
peratures and overall population density. Similarly, popula-
tion regulation has been shown experimentally to be cor-
related with the availability of food; supplemental feeding
results in population increases by as much as 500 percent,
due primarily to increased reproduction (i.e., fertility rates),
the survival of juveniles, and age at fi rst maturity. Yet there
is observational evidence to suggest that the digestibility of
food, rather than its quantity, is the more important proxi-
mal nutritional variable infl uencing juvenile survival. Forbs,
for example, are 30–40 percent higher in digestibility than
grasses. This suggests a tradeoff between reproduction and
survival in U. columbianus. Mortality in males is reported to
be higher during the mating season, and females that wean
young are more likely to die than those that lose litters.
Likewise, life-history models assume a tradeoff between
early and later reproduction; experimental manipulation
of litter sizes in one population, however, failed to find
evidence of any short-term relationship between current
and subsequent reproduction in U. columbianus. At least one
study suggests that if such a tradeoff exists, it may be depen-
dent on population size. Seven mammalian and three avian
species are reported to prey on Columbian ground squirrels.
This species distinguishes between rattlesnakes (Crotalus
viridis) and gopher snakes (Pituophis melanoleucus) and shows
more cautious behavior toward the former than the latter.
Experimental exposure to a potential predator (domesti-
cated dogs) results in higher cortisol levels in female ground
squirrels, unless the female is lactating, when cortisol levels
are normally low. Ectoparasites reported from the Colum-
bian ground squirrel include at least one tick, four mites,
two lice, and three fl ea species. Endoparasites consist of
only one species of Tr y p an o s o m a and three species of Eime-
ria. U. columbianus is a potential reservoir host for organisms
causing Rocky Mountain spotted fever, sylvatic (bubonic)
plague, and encephalitis. Experimental removal of ectopar-
asites from female squirrels resulted in better body condi-
tion during lactation and at weaning, as well as a larger lit ter
size, suggesting a signifi cant cost from an animal’s parasite
load.
general references: R. P. Bennett 1999a; Broussard,
Dobson, et al. 2005; Broussard, Risch, et al. 2005; Dobson
1992, 1994, 1995; Dobson and Oli 2001; Dobson, Risch, et al.
1999; Elliot and Flinders 1991; Festa-Bianchet and King 1991;
Hare and Murie 1992, 1996; Hubbs et al. 2000; K. Johnston
and Schmitz 1997; W. King et al. 1991; Manno 2008; Manno
et al. 2007; Menkens and Boyce 1993; Neuhaus 2000a, 2000b,
2003, 2006; Neuhaus, Bennett, et al. 1999; Neuhaus, Brous-
sard, et al. 2004; Neuhaus and Pelletier 2001; Stevens 1998;
Towers and Coss 1991; Weddell 1991.Urocitellus elegans Kennicott, 1863
Wyoming Ground Squirreldescription: U. elegans is a relatively small to medium-
sized ground squirrel, with big ears and a long tail. The up-
perparts are mixed gray, buff y, and dusky and are indis-
tinctly mottled. The sides of the head, neck, and body are
grayish, and are brownest dorsally. The belly is pinkish,
cinnamon, or buff y; the ventral surface of the tail is brown-
ish or buff y. This species is smaller than U. columbianus and
approximately the same size as U. armatus and U. beldingi,
which are both sympatric with U. elegans. The Wyoming
ground squirrel’s tail is longer and its ventral surface is more
buff y and less reddish than that of U. beldingi; and its ventral
surface is more buff y and less gray than that of U. armatus.
U. elegans is also sympatric with U. richardsonii and U. town-
sendii in some parts of its range, but it is distinguished from
the former by its consistently smaller body size and cranial
measurements, and from the latter by its larger size and
more cinnamon-colored venter.size: Female—HB 206.7 mm; T 73.1 mm; Mass 284.3 g.
Male—HB 204.8 mm; T 72.7 mm; Mass 329.9 g.
Sex not stated—HB 216.0 mm; T 73.5 mm; Mass 311.0 g.